A portable electronic device, such as a tablet computer, may include multiple speakers to provide a stereo audio presentation to a user of the device. In a stereo audio presentation, the audio signal that represents the left channel will be directed to speakers on the left side of the device as oriented with respect to the user. Likewise, the right channel signal will be directed to speakers on the right side of the device. The device may include four or more speakers symmetrically arranged on the device with respect to both the vertical and horizontal centerlines of a display surface to be viewed by the user. This will provide a generally similar stereo audio presentation to the listener in any of the four orientations of a rectangular device, if the sound is routed appropriately for the orientation.
It is desirable to route the audio signal that represents the left channel to all the speakers on the left side of the device to increase the maximum loudness and dynamic range, and to better center the apparent center of the sound field along the vertical axis of the device with respect to the listener. However, when the same audio signal is sent to two speakers, there will be a destructive interference of the resulting sound waves from the two speakers at certain places within the sound field produced. The locations of these areas of destructive interference are dependent on the frequency of the sound wave and the distance between the speakers.
It would be desirable to provide a way to minimize the destructive interference in the sound field of a portable electronic device in which the audio signal for each channel is routed to more than one speaker.